The American flag was hoisted over the New York in 1893 by President Harrison, and in the same year the British headquarters of the company were transferred from Liverpool to Southampton. In 1894 the first American-built ocean liner of the new fleet was launched, and was named the St Louis. In 1898 the American Line had the distinction of supplying the navy of its country with cruisers for use in war.

The St Paul, the only vessel of the four under contract in American waters at the time, was put under the command of Captain Sigsbee, whose own battleship, the Maine, had been blown up in Havana harbour on the 15th of February. The other three ships were also put into commission, the Paris being temporarily renamed the Yale and the New York the Harvard. In 1902 with their twin-screw liner Kensington the American Line made the first experiments towards fitting Atlantic passenger steamers with appliances for the use of liquid fuel.

The express fleet of the line consists of the four vessels, St Louis and St Paul, each of 11,600 tons and a length of 554 ft.; and the New York and Philadelphia, each of 10,800 tons and 560 ft. length. Several still larger but less speedy steamships have been constructed for the intermediate services of the company.

In addition to the weekly express service between Southampton and New York, the American Line runs steamers between New York and Antwerp, Philadelphia, Queenstown and Liverpool, and Philadelphia and Antwerp.